Philadelphia police have released a second suspect in a shooting that wounded two students at a charter high school.

Police haven't named the boy released, or another 17-year-old suspect who was charged with aggravated assault in the incident Friday afternoon at Delaware Valley Charter High School.

Police initially took a third suspect, a 15-year-old boy, into custody on Friday, but concluded he had nothing to do with the incident.

An 18-year-old girl was shot in the arm and the same bullet then hit a 17-year-old male. Both were treated at Albert Einstein Medical Center.

Police have suggested the shooting may have been an accident, but have yet to confirm that officially.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

A boy charged with aggravated assault and related crimes surrendered to police Saturday in connection with a shooting that wounded two students inside a Philadelphia high school gymnasium, authorities said.

Police were not releasing the 17-year-old suspect's name because it wasn't immediately clear if he was to be tried as an adult.

Police also didn't immediately identify another male suspect, whose age was not released. Although that boy surrendered Friday evening, police had yet to charge him, according to statements police released.

The shooting happened Friday about 3:30 p.m. at the Delaware Valley Charter High School in north Philadelphia. It remained unclear Saturday whether the shooting was accidental or intentional.

"A quick response by Philadelphia police allowed officers to immediately secure the school and determine this was not an active shooter incident," police said.

The wounded boy and girl each were shot in an arm, and by Saturday police confirmed that both had been hit by the same bullet.

The female student, 18, was shot in the rear of her left arm. "The bullet exited her bicep and then struck a 17-year-old male student in the shoulder," police said.

The female student was treated for her injuries and released from Albert Einstein Medical Center, while the male victim was admitted in stable condition, police said. The hospital could not provide additional information Saturday because police had not released the male victim's name.

Police Commissioner Charles Ramsey said police didn't know what staffing or security procedures were in place at the school but said "there was a breakdown in security of some kind" because the gun got into the building.

The school was placed on lockdown and secured by SWAT officers checking each room. Students were searched and released one by one.

A spokesman for the school district didn't immediately respond to a call seeking comment. The president of the charter school's board of trustees said he didn't have any additional information about the shooting.

Police said the suspects ran away after the shooting, and were identified after police reviewed school surveillance video. Police have yet to recover the weapon.

School officials and security officials initially identified a third student, 15, as a possible suspect.

"However investigators concluded that school security officials had provided inaccurate information to police concerning this young man, and he absolutely did not have any involvement in this incident," police said in one statement Saturday. "He was released and absolutely cleared by investigators."